Modeling Complex Inelastic Deformation Processes in IC Packages’ Solder Joints

Abstract

Large scale three-dimensional finite element analyses of 68 and 44 pin types Quad Flat I-Leaded packages subjected to −55°C to 150°C temperature cycling are performed to predict the way in which inelastic strains and microstructure evolve in the solder joints. A new set of unified constitutive equations, which correctly accounts for the inelastic strain rate dependency on stress, temperature, and microstructure (internal stresses) and the evolution of the latter with deformation, was used to model the solder joints’ thermo-mechanical behavior. Estimates of the critical inelastic strain ranges in the solder joints were obtained from the calculated inelastic deformation histories. The range of inelastic strain associated with each thermal cycle is small and practically unaffected by the observed ratcheting of the cycles toward positive strains due to the non-zero mean cycle stresses. By combining the numerical results with fatigue life data obtained from leads subjected to the same thermal loading, a fatigue life relation for mean failure probability of the IC packages’ solder joints has been proposed. The analysis correctly predicts the critical locations for crack initiation.

Influence of reflow and thermal aging on the shear strength and fracture behavior of Sn-3.5Ag solder/Cu joints

“…The effect of solder yield strength, intermetallic thickness, and intermetallic morphology have not been modeled in detail. [35,36,37] Here, we have used a two-dimensional model, shown in Figure 8, that consisted of the two Cu bars, and a Sn-3.5Ag solder interlayer. Since the objective of this part of the modeling was to understand the solder yield strength effects, the intermetallic layer was not included in the simulation.…”

Failure analysis of solder joints with a damage‐coupled viscoplastic model

“…At the local level, a comprehensive constitutive model is required to characterize the complex behaviour of solder under thermo-mechanical loads [1][2][3][4][5]. The development of this constitutive model is di cult due to the combination of elasticity, plasticity, creep, damage and micro-structural evolution that must be captured.…”

Constitutive Modeling of Viscoplastic Damage in Solder Material

“…For a reliability analysis, knowledge on the mechanical behavior of solder joints under thermomechanical loading is necessary. In past decade, many researchers have studied constitutive modeling and reliability of solder joints (Solomon, 1986, Busso, et al, 1994, McDowell, et al, 1994, Shine, et al, 1994, Frear, et al, 1997, Lau, et al, 1997and Shi, et al 1999. However, the previous work focuses on either the experimental results or the conventional analytical approaches based on the assumption that all materials are perfect or defects-free during a loading process.…”